1. Field of Invention
The present invention relates to a liquid crystal display (LCD) structure. More particularly, the present invention relates to a reflective and transflective type of liquid crystal display or liquid crystal display structure with excellent legibility and display efficiency.
2. Description of Related Art
In recent years, the applications of liquid crystal display (LCD) are far and wide following full integration with various electronic device packages. Functional capacity and complexity of typical LCD such as liquid crystal monitors and PDAs also expand with time. In general, LCD devices may be categorized into three major types, namely, the reflective type, the transmissive type and the transflective type.
FIG. 1 is a cross-sectional view of one conventional pixel portion of the transflective liquid crystal display device. As shown in FIG. 1, the liquid crystal display device includes an upper glass panel 10a, a lower glass panel 10b, an upper polarizing film 11a, a lower polarizing film 11b, an electrode structure 12, a liquid crystal layer 14, a color filter 16, a transparent conductive layer 20, an organic insulating layer 26, a thin film transistor 28 and a back light system 29. The upper polarizing film 11a is on the upper surface of the upper glass panel 10a and the lower polarizing film 11b is on the lower surface of the lower glass panel 10b. The electrode structure 12, the liquid crystal layer 14, the color filter 16 and the transparent conductive layer 20 are all enclosed within the space between the upper glass panel 10a and the lower glass panel 10b. The electrode structure 12 is composed of a reflective electrode 22 and a transmissive electrode 20. The transmissive electrode 20 can be, for example, an indium-tin-oxide (ITO) layer. The color filter 16 is a layer formed on the interior flat surface of the upper glass panel 10a. Meanwhile, the electrode structure 12 is formed on the interior flat surface of the lower glass panel 10b. The organic insulating layer 26 underneath the reflective electrode 22 has an uneven surface. The surface of the organic insulating layer 26 includes a plurality of protrude/recess structures 26a (or bumps). The thin film transistor (TFT) is formed over the lower glass panel 10b. The thin film transistor 28 includes a gate electrode 28a, a source terminal 28b and a drain terminal 28c. The back lighting system 29 is mounted on the exterior surface of the lower polarizing film 11b. 
To increase the efficiency of reflection in FIG. 1, the protrude/recess structure 26a of the organic insulating layer 26 is specially designed to have an undulating surface. Due to the non-planarity of the reflective electrode 22 surface, liquid crystal misalignment and non-uniformity of liquid crystal cell gap inside the pixels can be detrimental to the display performance. Ultimately, quality of the liquid crystal display product is compromised. From FIG. 1, the reflective electrode 22 has an undulating shape and is made of a material having a high light reflection efficiency. When light is emanated from the back light system 29 behind the liquid crystal layer 14, the light passes through the liquid crystal layer 14 only once and exits out from the display surface. When a beam of light incident on the surface of the liquid crystal display from the viewer's side, the light passes through the liquid crystal layer 14 and is reflected by the reflective electrode 22 having the undulating shape, and passes through the liquid crystal layer 14 again to exit from the surface of the liquid crystal display. The light is reflected at various angles due to the undulating shaped reflective electrode 22. The incident/reflection angles are measured with respect to the normal of the transparent substrate 10b (i.e. the line perpendicular to the surface of the transparent substrate 10b) in the plane of 6 o'clock and 12 o'clock. From experimental measurements for an incident light 30° from normal in the 12 o'clock direction, the light beam reflected from the display in a range between 0° and 30° in the 6 o'clock direction is the most effective condition for a viewer. When the reflective angle of the light beam greater or less than this range, the viewing condition is poor for the viewer.
Hence, reflected lights at various angles outside the range are not effective for viewing. The reflected lights at various angles are reflected from various parts of the undulating surface of the reflection electrode. Therefore, if we only utilize the portions of the reflector surface which contributes to the useful reflected lights and convert the nonuseful parts of the reflector into transmissive region by removing the reflectors, the efficiency of the LCD can be significantly improved.